linux-kernel - RE: [PATCH] x86/hyperv: Suspend/resume the VP assist page for hibernation

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Message-ID: <HK0P153MB027347CE9D0C35A1C53B19F6BFD40@HK0P153MB0273.APCP153.PROD.OUTLOOK.COM>
Date:   Mon, 20 Apr 2020 16:40:54 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Wei Liu <wei.liu@...nel.org>
CC:     "bp@...en8.de" <bp@...en8.de>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        vkuznets <vkuznets@...hat.com>
Subject: RE: [PATCH] x86/hyperv: Suspend/resume the VP assist page for
 hibernation

> From: Wei Liu <wei.liu@...nel.org>
> Sent: Monday, April 20, 2020 5:08 AM
> 
> I would suggest make this clear in the commit message to not give the
> impression that Hyper-V has this weird behaviour of corrupting guest
> memory for no reason.
> 
> We can replace the paragraph starting with "The issue is: ..." with:
> 
> ---
> Linux needs to update Hyper-V the correct VP assist page to prevent
> Hyper-V from writing to a stale page, which causes guest memory
> corruption.  The memory corruption may have caused some of the hangs and
> triple faults we saw during non-boot CPUs resume.
> ---
> This What do you think?

This version is much better. I'll use it. Thanks, Wei!

I'll post a v2 with the updated comments. I'll document Vitaly's concern about
nested virtualization in the comment.
 
Thanks,
-- Dexuan